Merge pull request #707 from desihub/ADM-zcat-dchisq

When making a zcat, update the ZWARN bit-mask using DELTACHI2 values

doc/changes.rst

@@ -5,7 +5,11 @@ desitarget Change Log
 0.57.1 (unreleased)
 -------------------
 
-* No changes yet.
+* When making a zcat, update ``ZWARN`` using ``DELTACHI2`` [`PR #707`_]:
+    * Flag ``ZWARN`` for all targets with ``DELTACHI2 < 25``.
+    * Also flag ``BGS`` targets in bright-time with ``DELTACHI2 < 40``.
+
+.. _`PR #707`: https://github.com/desihub/desitarget/pull/707
 
 0.57.0 (2021-04-04)
 -------------------

py/desitarget/data/targetmask.yaml

@@ -175,7 +175,7 @@ targetid_mask:
     - [RESERVED,   62, "RIGHTMOST bit for left over bit space (encompasses bit 62 inclusive)",           {nbits: 1}]
 
 # ADM ZWARN mask (bits that can be set to warn that a redshift is bad).
-# ADM inherited from https://github.com/desihub/redrock/blob/8e33f642b6d8a762c4d71626fb3aca6377c976d4/py/redrock/zwarning.py
+# ADM inherited from https://github.com/desihub/redrock/blob/master/py/redrock/zwarning.py
 zwarn_mask:
     - [SKY,                0, "sky fiber"]
     - [LITTLE_COVERAGE,    1, "too little wavelength coverage"]
@@ -188,6 +188,9 @@ zwarn_mask:
     - [BAD_TARGET,         8, "catastrophically bad targeting data"]
     - [NODATA,             9, "No data for this fiber, e.g. because spectrograph was broken during this exposure (ivar=0 for all pixels)"]
     - [BAD_MINFIT,        10, "Bad parabola fit to the chi2 minimum"]
+    - [LOW_DEL_CHI2,      16, "DELTACHI2 is lower than 25 for a DESI SV3 target"]
+    - [LOW_DEL_CHI2_BGS,  17, "DELTACHI2 is lower than 40 for a DESI SV3 BGS target in bright time"]
+
 
 #- Priorities for each target bit
 #- Numerically larger priorities are higher priority to be observed first.

py/desitarget/mtl.py

@@ -909,8 +909,8 @@ def tiles_to_be_processed(zcatdir, mtltilefn, obscon, survey):
     return newtiles
 
 
-def make_zcat_rr_backstop(zcatdir, tiles):
-    """Make the simplest possible zcat using SV1-era redrock outputs.
+def make_zcat_rr_backstop(zcatdir, tiles, obscon, survey):
+    """Make a simple zcat using only redrock outputs.
 
     Parameters
     ----------
@@ -920,6 +920,14 @@ def make_zcat_rr_backstop(zcatdir, tiles):
         Numpy array of tiles to be processed. Must contain at least:
         * TILEID - unique tile identifier.
         * ZDATE - final night processed to complete the tile (YYYYMMDD).
+    obscon : :class:`str`
+        A string matching ONE obscondition in the desitarget bitmask yaml
+        file (i.e. `desitarget.targetmask.obsconditions`), e.g. "DARK".
+        Governs how ZWARN is updated using `DELTACHI2`.
+    survey : :class:`str`, optional, defaults to "main"
+        Used to update `ZWARN` using `DELTACHI2` for a given survey type.
+        Options are ``'main'`` and ``'svX``' (where X is 1, 2, 3 etc.)
+        for the main survey and different iterations of SV, respectively.
 
     Returns
     -------
@@ -987,6 +995,19 @@ def make_zcat_rr_backstop(zcatdir, tiles):
     for col in set(zcat.dtype.names) - set(['RA', 'DEC', 'NUMOBS', 'ZTILEID']):
         zcat[col] = zs[col]
 
+    # ADM Finally, flag the ZWARN bit if DELTACHI2 is too low.
+    if survey == "sv3":
+        from desitarget.sv3.sv3_targetmask import desi_mask
+        desi_target = fms[zid]["SV3_DESI_TARGET"]
+        # ADM set ZWARN flag for everything with DELTACHI2 < 25.
+        lodc2 = zs["DELTACHI2"] < 25
+        zcat["ZWARN"] |= lodc2*zwarn_mask["LOW_DEL_CHI2"]
+        if obscon == "BRIGHT":
+            lodc2 = zs["DELTACHI2"] < 40
+            bgs = desi_target & desi_mask["BGS_ANY"] != 0
+            lodc2bgs = bgs & lodc2
+            zcat["ZWARN"] |= lodc2bgs*zwarn_mask["LOW_DEL_CHI2_BGS"]
+
     return zcat
 
 
@@ -1069,7 +1090,7 @@ def loop_ledger(obscon, survey='main', zcatdir=None, mtldir=None,
 
     # ADM create the zcat: This will likely change, but for now let's
     # ADM just use redrock.
-    zcat = make_zcat_rr_backstop(zcatdir, tiles)
+    zcat = make_zcat_rr_backstop(zcatdir, tiles, obscon, survey)
 
     # ADM insist that for an MTL loop with real observations, the zcat
     # ADM must conform to the data model. In particular, it must include